Summary of lecture 1/24/00

1. Summary of lecture 1/24/00 • A new fundamental force: • Gravity keeps us on earth • Electrostatic forces keep us together • Two types of charge (+,-) that generally cancel on macroscopic scale • When balance is disturbed we see attraction and repulsion from electrostatic force. • Coulombs law: • Charge is conserved and quantized in units • Charged objects attract neutral objects through polarization

2. Summary of Lecture 1/31/00 • Charge transport in matter: • Insulator : No macroscopic charge motion • Conductor : electrons move with ease • Semiconductor : Either of the above • Superconductor : Charge moves with no “friction” • E(r) characterizes “conditions” around charged object as measured with “test charge” q • Electric field from a point charge: • Electric field far from dipole r, q +Q -Q +Q d z

3. Summary of Lecture 2/1/00 v0 • Charge moving through uniform electric field: Projectile motion but • Electric dipole ( ) “lines up” //Electric field: • Electric field from continuous charge distribution • Calculated E(r) along normal to charged line segment Q E r(r’) R r’ r